David Wagner does not call it heavy metal football. The former Borussia Dortmund reserve team manager, who was convinced to become a coach by his former Mainz team‑mate and great friend Jürgen Klopp, prefers to use a different term for the style of play he has been cultivating at Huddersfield Town since being hired in November with instructions to transform the club.

“We now call it the Terriers’ identity,” says Wagner with a broad smile. “Exactly the style of football I love is like a terrier. We are not the biggest dog, we are small, but we are aggressive, we are not afraid, we like to compete with the big dogs and we are quick and mobile and we have endurance. We never give up. This small dog has fighting spirit for sure.”

Five games into the season and this small dog is top of the Championship, having sunk its teeth into two of the favourites for promotion, winning at Newcastle United and drawing at Aston Villa. No one at Huddersfield is barking about promotion to the Premier League yet, nor even about ending the season higher than Saturday’s opponents, Leeds United, for the first time since 1962. Nor is anyone ruling it out. “I don’t set targets because sometimes targets are limits and we don’t like limits,” says Wagner. “But I’m not a dreamer, I’m a worker.”

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Wagner makes sure his players work, too, so that they can play at the ferocious intensity he demands. He introduced double training sessions as soon as he arrived, with start times switched to correspond to the kick-off of the next match, whether at 3pm or in the evening. Pundits warned of mutiny but Wagner has found harmony. “This was one of the biggest surprises and biggest helps for me,” he says. “There was no resistance, especially from the very experienced players like Dean Whitehead and Mark Hudson. If you deliver professionals something that makes them feel stronger, then they will follow. This was the case and this was the reason why they are very open for the future.”

Huddersfield’s performances improved rapidly under Wagner but they appeared to run out of steam towards the end of last season, which concluded with a 4-0 loss at Bristol City and a 5-1 home defeat by Brentford. Wagner knew that his first pre-season with the club would be crucial, especially after he bought or brought in on loan 13 players, including four from Germany, where Wagner was born and bred before playing internationally for the United States, his father’s homeland. Wagner needed to fuse these players rapidly into a unit so on the first day of pre‑season training, before any fitness or tactical work, he took them to fend for themselves on a tiny uninhabited island off the coast of Sweden.

“We knew we had a lot of new signings and should never forget that this is a traditional English football club with more than 100 years of history and I am the first manager from outside the British Isles and maybe there are as many foreign players as there has ever been, so we thought: ‘How can we make the players bind together very quickly?’” he says.

“We went to Sweden for four days and three nights and we didn’t bring a ball. We were really in the wild, no electricity, no toilet, no bed, no mobile phone or internet. If you are hungry, take your rod and get a fish. If you are thirsty, go to the lake and put your bottle in. If you are cold, make a fire.

“We had three guides with us to help, but if you are always together, in a two-man tent or eight hours a day in a two-man canoe – and we always rotated the pairings – then you have to speak to each other. I am convinced that the better you know your mate off the pitch, the more you are able to work for him on it in uncomfortable situations.

“They changed their borderlines over those three days. I can say now, three months later, that it was 100% success, and that is the feedback from the players, too.”

Wagner is no hollow sergeant‑major. He laughs a lot for a start and his approach is rooted in more than an ability to foster a strong esprit de corps. He has overseen the appointment of a nutritionist and a head of performance services and has had it written into players’ contracts that they must live within 15 miles of the club’s training ground because long commutes hinder recovery. These are basic measures for a man who spent five years gaining a degree in biology and sports science from Darmstadt University after finishing his playing career in 2005.

“Maybe I can say I lost my hunger for the football business so I decided to study to understand more about the science side,” he says of that career move. “Those were probably the hardest five years of my life, but I did it. After about two years, my hunger for football came back.”

David Wagner at Huddersfield’s training ground. Photograph: Matthew Lloyd for The Guardian

Klopp, who is godfather to one of Wagner’s children, helped keep his hunger alive. “Jürgen said to me one day shortly before I did my last exam: ‘Listen, you were a professional footballer so when you get your exam, please do your Uefa pro licence, then you will have the three qualifications you need and all doors will be open for you to come back into football.’”

That is what Wagner did, but after completing his pro licence and running Hoffenheim’s under-19s for two years, he decided to go back to school. He was 18 months into the two years of practical work experience required to qualify as a teacher in Germany when, in 2011, Klopp asked him to coach Dortmund’s second team. “I had a few discussions at home,” says Wagner. “Then I decided to take the job.”

He thrived at it for four years, taking Dortmund II to the third tier of German football while playing the exhilarating style that Huddersfield’s chairman, Dean Hoyle, would eventually ask him to transplant to Yorkshire.

“The main part of the style here is exactly what we had in Dortmund,” says Wagner. “We have had to adapt some things to the English environment. For example, referees here do not blow their whistles as much so there are fewer breaks in the game and players get more tired around 70 minutes. Maybe sometimes we have to keep the ball more rather than go for another goal even if you might then concede an equaliser.”

Mostly, however, Huddersfield play like a whirlwind. The exciting style was one of the reasons why the club sold a record number of season tickets this summer, more than 15,000 (the other reason was that Hoyle slashed prices). In August, the club enjoyed its highest attendance on an opening day for 46 years and 18,479 fans were thrilled to witness evidence that Wagner’s pre-season had paid off as Huddersfield avenged their heavy loss on the final day of last season by beating Brentford 2-1.

That fine start to the campaign has continued. Huddersfield even won 2-1 at Melwood last week when Klopp invited them to play a friendly behind closed doors against Liverpool players who were not on international duty.

The question now is whether Huddersfield can sustain their all-action style over a 46-match league campaign without a winter break. “There’s no reason why not,” says Wagner. “The important thing is to find the right balance between intensity and recovery and everybody knows I have no problem with rotation.” But Wagner reiterates: “There are a lot of different areas where we have to go forward to be a proper professional football club and we are only at the start of his journey.”

He adds: “But we can enjoy our start and be confident as we go into the biggest game of our season, against Leeds United. It’s not just a derby, for us it’s the derby.” Wagner reckons March’s 4-1 win at Elland Road could be the highlight of his reign so far. “We will do our best to make our fans celebrate again,” says a man who is changing his club’s identity, but not too much.